Gaseous electric discharge lamp



June 27, 1961 9 R. V. HEINE-GELDERN GASEOUS ELECTRIC DISCHARGE LAMPFiled Feb. 10, 1958 INVENTOR.

ROBERT V. HElNE-GELDERN BY KWQ/MU ATTOR EYS United States Patent Q iJersey Filed Feb. 10, 1958, Ser. No. 714,189 2 Claims. (Cl. 313-54) Thepresent invention deals with gaseous electric discharge lamps of thehigh pressure type.

A light source such as a tungsten filament incandescent lamp producesfull illumination almost immediately because the time required to heatthe filament to full brilliancy is less than one second. Commercialfluorescent lamps operating with mercury vapor at very low pressures,e.g. 0.015 millimeter, require less than one-half minute to reach fullbrightness. With commercial high pressure lamps and super high pressurelamps which require the attainment of mercury vapor pressures from about300 to 60,000 millimeters, depending on the type of lamp, a time elapseof several minutes to about onehalf hour may be required to reach fulllight output. Lamps of this type employ metals such as mercury, cadmium,sodium, caesium and the like for providing the metal vapors in whichduring operation, the electric discharge occurs. At room temperatures(25 centigrade) these metals are mostly either in a liquid or solidcondi tion and have in the vapor phase pressures of less than about0.002 millimeter on the mercury scale. As a result, when such lamps arestarted there is a very appreciable time period during which the metalsmust be evaporated and raised to high pressure vapor conditions. Duringthe beginning of this period the lamps produce very little usefulillumination.

The employment of mercury and a rare gas in the same lamp is not new.Rare atmospheric gases such as xenon, neon, argon and krypton at a fewto about 150 millimeters pressure have been used in mercury lamps forpurposes of starting the lamps and of providing the initial evaporationof the mercury. In these lamps the contribution of the rare gas to thelight output of the lamp is entirely negligible. During the first fewminutes of operation such lamps produce less than one percent of theirultimate average brightness. For some applications this behavior is notobjectionable, eg for street lighting and the like, but for otherapplications the initially low light output and brightness of theselamps makes them impractical.

Super high pressure rare gas lamps operate with an efiiciency whichcannot be approached by filament type lamps and have a unit brightnessgreatly in excess of other light sources. Hence, they are desired forvery many applications. These lamps, however, are difficult to igniteand require complicated starting equipment such as high voltage radiofrequency apparatus to produce some ionization to facilitateestablishment of the are.

It is an object of the present invention to provide a high pressure andespecially a super high pressure gas discharge lamp capable of producingbrilliant light immediately upon starting.

It is another object of the invention to provide a high pressure gasdischarge lamp containing a combination of gases as an atmosphere andwhereby the gas combination facilitates ignition of the lamp. Otherobjects of the invention will become apparent from the descriptionhereinafter following and the drawing forming a part hereof 2,990,499Patented June 27, 1961 which represents an elevational view of a lampembodying the subject matter of the invention.

The present invention applies to compact arc type lamps in which thefinal or operating vapor pressure exceeds about 10,000 millimeters andwhich have short discharge paths of the order of one centimeter andless. It also applies to lamps of the capillary type containing highpressure gas and spaced electrodes which may exceed one centimeterspacing. The ionizable filling of the lamp according to this inventionconsists of a rare gas at a pressure between 1 and 20 atmospheres atabout 25 centigrade or such gas together with a vaporized metal in anamount sufiicient to become completely vaporized during the operation ofthe lamp together with a radioactive gas at a partial pressure less thanthat of the main rare gas component. The lamp is from the moment ofstart always a high pressure discharge lamp. The envelope contains a gasfilling preferably of xenon gas at a pressure between 1 and 20atmospheres. If one provides a lamp of the above named types with a highpressure gas filling of xenon and in addition, with a radioactive gas,especially radioactive krypton in an amount suificient to provide aradioactivity of up to 200 microcuries, one can obtain substantiallyimmediate starting of the lamp at 25 C. approximate ambient temperaturewithout complicated starting equipment.

Referring to the illustration, the lamp is a compact type lampcomprising either a substantially spherical or elliptical lighttransmissive envelope 1 to provide the required strength and made offused quartz or a high temperature glass, since it must withstandoperating temperatures of the order of 1200 Kelvin. The envelope 1 isprovided with tubular extensions, e.g. tubes 2 and 3 projectingoutwardly therefrom preferably oppositely of each other, which support apair of spaced electrodes 4 and 5, which are preferably tungstenelectrodes in solid or coiled form and spaced from each other. The otherstructures such as the reflecting members 6 and 7, the vacuum-tightseals 8 and 9, and the terminals 10 and 11, are merely illustratory forpurposes of the present invention and are intended to show a type oflamp unit to which the essential embodiments of the invention areapplicable.

The electrodes 4 and 5 which are provided to supply electric power tothe gas are which forms between them, are spaced from each other at adistance of the order of one centimeter and less.

The envelope 1 contains a rare gas, e.g. xenon, at a pressure between 1and 20 atmospheres at about 25 centigrade together with a radioactivegas, e.g. radioactive krypton, in an amount suiiicient to provide aradioactivity of up to 200 microcuries, which would function to keep thelamp ionized and still safe for ordinary storage, operation andhandling. The radioactivity of commercially available krypton is about21,000 millicuries per gram so that about five to ten micrograms yieldsan activity of from about to 200 microcuries, which is adequate forproviding sufiicient ionization of the lamp atmosphere to facilitate theinitiation of an arc discharge upon the application of electricalenergy.

While the lamp as illustrated is a compact arc lamp, other type highpressure and super high pressure are lamps are contemplated within thescope of the appended claims.

What is claimed is:

1. A high pressure gaseous discharge lamp comprising a lighttransmissive envelope containing spaced electrodes a f p H 2,990,490 I 3a a e 7 a and an ionized atmosphere, the ionized atmosphere com-References Cited in the file of this patent prising a rare gas at apressure of from 1 to 20 atmospheres "and mercury in an amountsuflicient to become UNITED STATES PATENTS completely vaporized duringthe operation of the lamp 2,670,451 F eman et a1, Feb. 23, 1954 and fromabout five to ten micrograms of a radioactiv 5 2,673,944 Francis Mar.30, 1954 gas to provide up to 200 microcuries of radioactivity.2,716,713 Noel Aug. 30, 1955 2. A high pressure gaseous discharge lampaccording to claim 1, .wherein the radioactive gas is radioactiveFOREIGN PATENTS krypton. V 737,386 Great Britain Sept. 28, 1955

